Wearing of a head covering Kippot,
yarmulka, skullcaps,
kippah for men was only instituted in Talmudic
times The first mention of it is
in Tractate Shabbat, which discusses respect and fear of God.
Some sources likened it to the High Priest who wore a hat (Mitznefet)
to remind him something was always between him and God. Thus, wearing a
kippot makes us all like the high priest and turns us into a "holy
nation." The head covering is also a sign of humility for men,
acknowledging what's "above" us (G­d).

Many Ashkenazi rabbis acknowledge that wearing
Kippot
covering at all times was once considered an optional midat chasidut
(pious act), but, today, full­time head covering is the norm except
under extenuating circumstances. Sephardic communities generally did not
have the custom of wearing a kippah all the time.

Some diaspora Jews leave off the yarmulkas at school,
work, or when testifying in court, because of real danger or uneasiness
in appearing in the secular world with an obvious symbol of Jewishness.

In Israel wearing Kippot also has a social
significance. While wearing a
kippah
shows that you are somewhat
religious, not­wearing one is like stating, "I'm not religious." The
style of kippot in Israel can also indicate political and religious
affiliations. Classical orthodoxy uses a large, smooth, black one shaped
like a bowl. Many Hasidim use large black felt or satin, and a
"rebellious son" may wear a slightly smaller black
SkullCaps to show his
independence while remaining in the Classicist camp. Another play on
this rebellion is to wear knitted black kippot. This is also usually
used to confuse people as to where you stand.

In Bukhara and the Caucasian Mountains the use of
large brightly woven
yarmulkas is common. It is similar in shape to a
cantor's
yarmulka without the peak. This custom can also be found in other
Sephardic communities.

Knitted
kippot typically signify that you are part of
the Nationalist Zionist camp. A larger full headed knitted kippah would
signify the Mercaz Harav branch of the movement that produces many of
the leading rabbis within the Religious Zionist section, although many
rabbis who teach at these institutions wear the traditional large black
kippot.